Pneumatic loud speaker



Feb. 21, 1933. F L HETZEL 1,898,302

PNEUMATIC LOUD SPEAKER Filed Sept. 25, 1930 2 Sheets-Sheet l Feb. 2l, 1933. F, L HETZEL 1,898,302

PNEUMATIC LOUD SPEAKER Filed Sept. 26, 1930 '2 Sheets-Shqet 2 l Patented Feb. 21, 1933 UNITED sine'lzssv FRANK L. HETZEL, OF `EIIIEBCIMIOSA. BEACH, CALIFORNIA PNEUMATIC LOUD SPEAKER Application led September 26, 1930. Serial No. 484,608.

This invention relates to loud speakers of the pneumatic type which include in their construction an air valve to which vibrations are imparted. The general object of the invention is to provide a pneumatic loud speaker of improved construction and having improved means for effecting the vibration of the air valve.

A further object of the invention is to improve the general construction of air valves of the grid type and toprovide improved means for adjusting the grids relativelykto each other.

A further object of the invention is to produce an air valve of simple construction and capable of receiving vibrations capable of producting sound, whether produced by a sound-translating device or through the '25 agency of a record.

Further objects of the invention will appear hereinafter.

The invention consists in the novel parts and combination of parts to be described hereinafter,` all of which contribute to produce an eiiicient pneumatic loud speaker.

A preferred embodiment of the invention is described in the following specification, while the broad scope of the .invention is pointed out in the appended claims.

In the drawings:r

Figure l is a vertical section through the upper portion of the apparatus embodying my invention, certain vparts being broken 5 away.

Figure 2 is a side elevation ofthe same apparatus upon a reduced scale, certain parts being broken away.

Figure 3 is an ideal horizontal section through the apparatus taken about at the level of the line 3 3 of Figure 2 but upon an enlarged scale, certain parts vbeing' broken away. v

Figure 4 is a horizontal section taken about on the line 4-4 of Figure2, and particularly illustrating the construction of the electrodynamic means for imparting vibrations to the air valve.

Figure 5 is a vertical section taken about on 5 the line 5-5 of Figure 2;

Figure 6 is a front elevation of the relatively movable grid of the air Valve showing a portion of the fixed grid broken away. Before describing the invention detail, it should be` stated that in the present specication I have described the apparatus as constructed so that the air valve is vibrated through an electromagnetic vibrating device, but it should be understood that in practice the air valve can be vibrated by any other means, for example, a phonograph record. So far as the air valve is concerned, it is merely necessary to impart the vibration corresponding to the sounds it is desired to reproy duce in the loud speaker. My invention, how- 5* ever, coIlCClns the electromagnetic means as Well as the air valve and its connections to the horn of the loud speaker.

Referring more particularly to the parts, l represents an electromagnetic vibrating device which may have some of the features of construction of a magnetic speaker that is to say, it may include a large permanent U- shaped magnet 2 between the lforks of which laminated pole pieces 3 are mounted, and be- 75 tween these 'pole pieces a gap 4 is formed to receive an oscillator or armature 5 in the form of a bar of magnetic metal, said oscilla 4 tor being preferably mounted on ailexible bridge or bridge bar 6. (See Fig. 4.) The 80 plates of the laminated pole pieces 3 are cut away in the usualmanner to form projecting pole pieces or forks 7, thereby forming a relatively -large gap 8 which receives thevoicecoil 9 'of the device. When the device is in 85 use, this coil has its terminals l0 connected; into the sound controlled circuit over which the electric impulses 'come that have been iniuenced or produced through the agency of sounds. l n 90 The oscillator 5 is providedwith a dampener de'.ice in the form of a link 11 consist- `ing of a thin plate which is attached tov one end of the oscillator 5 and extends across to one side where it is securedlto an adjustable anchor plate or anchor bar 12. This anchor bar is adjustable4 in a longitudinal direction to adjust thel position of rest of thepscilla'- tor 5,.. According to my invention I provide for dampening the vibrations of the oscilla- 10 terial. These pads 13 are clamped between the head 13a of a clamping bolt and an adjustable washer 13b on the threads of the clamping bolt. The upper end of the anchor bar is slotted to receive the clamping bolt.

By adjusting the bolt and washer it will be evident that the position of the anchor bar can be regulated as well as the degree of dampening.

The pneumatic apparatus of this device is preferably mounted above the electromagnetic mechanism as indicated in Figure 1 and preferably includes a frame 14 with an integral tubular sleeve 15 to one side of which the horn 16 of the loud speaker is attached. The mechanism also includes a sound box 17 in the form of a rectangular or box-like casing having an opening 18 at one side for the admission of compressed air. ,At/another point `the sound box is provided with an outlet opening 19 at which the air valve 2O is located. This air valve preferably consists of a relatively fixed grid 21 `and a relatively movable grid 22. The grid 21 `is rigidly secured on the face of the sound box, preferably by clamping it into position in the manner indicated in Figure 3. That is to say,

this grid is in the form of a plate clamped` between a tubular fitting 23 and the face of the sound box. If desired they-grid 21 may be sweated tothe forward wall of the box.

The sound box is preferably not rigidly supported, but is mounted so4 that ,it is capable of slight movements on a horizontal axis. For this urpose the sound box is preferably supported from its rear wall on a back leg 24 mounted on gudgeons Y25 placed in upwardly projecting vears or brackets 26 that project up from the base plate of the frame 14.A y

The upper end of this back leg i's provided with a slot as indicated at 27 which receives an adjusting stud 28 that projects from the rear wall of the sound boxand receives a wing nut 29 for clamping the parts in any' desiredadjusted position. The air valve is constructed with 'openings in the movable grid o f larger size than thosev in the other 1 f The relatively fixed grid 21 has aplurality of vsubstantially parallel outlet 4slots 30, and similar slots 31, but of greater width, are

formed in the relatively movable grid 22. This relatively movable grid 22 is constructed yso that it will be light but with considerable rigidity. 'For this purpose I -prefer to construct it of duralumin and provide itwwith stiienin ribs 32/on its outer face lying between t e slots' The slots 31 should be Aaligned midway between the 'slots 30 and the relatively movable. grid normally lies flat agalnst the face of the fixed grid. The movthe direction of the slots. In this connection reference is had to Figures 1 and 5 in which the lower portion of the movable grid is indicated as provided with a downwardly projecting extension or arm 33.

There should be one more of the slots 30 than the slots 31. This appears to be important and the movable grid should be adjusted so that its slots 31' are exactly midway between the slots 30.

At its upper portion this extension or arm 33 is extended laterally to form a relatively large foot 34 which is attached to the under side of a flexibleV rocker or vibrating plate 35, the ends ofvthis plate being received on flat seats 36 and provided with slots at 37 to receive clamping screws 38. The ends of the late are in line with adjusting setscrews 39 t at screw into lugs 40 projecting down from -the sound box (see Fig. 2). Evidently fixed vgrid or seat of the air valve. This .means may be in the form of two pins 36a (see Fig. 5) that project down from the botvtom of the sound box.

The lower end of the extension 33 carries' astylus 41 which ma be clamped in place by a clamp screw 42. f desired, this stylus 41 may be made as an integral extension of the upper end' of the oscillator 5. I prefer, howl:

ever, to rovide the upper end of the oscillator 5 wlth a stem 43 of reduced diameter surmounted by a head 44 from which the stylus 41 extends upwardly.

If desired, this stylusjcan be made as a separate part from the oscillator 5 and provided with a point at its lower end recelved in a small socket formed in the upper face ofthe head 44. v f

l"The 'sound box is vpreferably pressed downwardly toward its forward side by a fiat spring 45. (see Fig. 1), which spring is'anchored `on a pivot screw 46 and passes through-a guide slot 47 in an integral iin 48 projecting up from the upper side of the tubular sleeve 15. .By swinging this spring 45' 15 a gap 49 should be formed to prevent metallic connection directly from the part 23 tothe horn 16. This prevents vibration of the horn being imparted metallically to the valve. However, vthis gap 49 is preferably closed by a pliable sleeve orA band 50 of rubberor similar soft material that is not adapted toy transmit vibrations.

The base plate of the bracket 14 has a slo 51 formed through it through which the upper end of the l oscillator -5 extends.

The adjustment for the oscillator 5 may include an adjusting screw 52 (see Fig. l), the head of which carries a collar 53 that is secured to the lower end of the anchor bar l2 referred to above. By loosening up on the thumb head 54 that clamps the dampers 13 against the anchor plate, this screw 52 may be adjusted up or down so as to tilt the oscillator 5 on the longitudinal axis of the bridge plate 6.' In this Way lsuitable adjustments in this regard can be made. The damper cushions should be operated to cooperate with the adjusting screw 52 in affecting such adjustments.

The under side of the fitting or throat piece 23 may be provided with an opening or throat 55 through which the moyable grid 22 can be put in place from below.

In the operation of the device, when electric impulses pass through the coil 9 they cause oscillation in a vertical plane of the oscillator 5, these oscillations correspond in period to th-e pulsations or impulses of the current passing through the coil. In this way vibrationis imparted to the movable grid 22 of the air valve corresponding to the di'erent sounds. This opens the air valve more or less and permits the air under pressure to escape through it into the horn. The air takes up the vibration of the movable grid and the sound can bev reproduced with an extraordinary amplification of its volume. i

rIhe compressed air I have employed gave satisfactory results at pressures between 7' and 25 pounds per square inch.V If the air valve is to be operated byl 'a phonograph record, a regular phonographneedle or stylus is substituted for the stylus 41, its lower end being pointed and running in the record oove.

It should be noted that the pliable connection 50 cooperates with the spring 45 to permit' free movement of the fitting 23 and sound vbox independent of therigid horn sleeve 15.

Itis understood that the embodiment of the invention described herein is only one of the many embodiments this invention may take, and I do not wish to be limited in the practice of the invention, nor in the claims,'to the particular embodiment set forth.

What I claim is: v

l. In a pneumatic loud speaker, the combination of an air valve with arelatively fixed grid and a movable grid opposite the relatively fixed grid, an electromagnetic vibrator de,- vice having a voice coil and an oscillator mounted for vibration by the said coil and connected with the movable grid to oscillate it toward and from the relatively fixed grid.

-2. In a pneumatic loud speaker, the combination of a relatively fixed grid and a relaslots therein seating against theface` of the fixed id and with the slots of the relatively mova le grid out of line with the slots of the relatively fixed grid, means for supporting the relatively movable grid to rock toward or from the relatively fixed grid, an electromagnetic vibrator device having a voice coil, and an oscillator, mountedfor vibration by thesaid coil and connected with the relativev ly movable grid for vibrating the same.

4. In a pneumatic loud speaker, the combination of a relatively fixed slotted grid and a relatively movable slotted grid mounted to seat on the first-named grid, means for supporting the movable grid to enable the same to rock toward or from the fixed grid, an actuating arm carried by the movable grid, an electromagnetic vibrator device having a voice coil, and avibrator mounted for vibration by the said coil and connected with the said actuating arm for vibrating the movable grid.

5. In a pneumatic loud speaker, an air valve'having a relatively fixed grid with outlet openings therein, a movable grid seating on the face of the fixed grid and having outlet openings therein of larger dimensions than the openings in the fixed grid and seating on the face ofthe fixed grid so that the openings of the movable grid are out of alignment with the openings of the fixed grid, and means Jfor vibrating the movable grid.

6. An air valve constructed as described in claim 5 in which the outlet openings in the grids are inthe form of substantially parallel slots with the slots of the relatively movable grid of greater width than the slots in the fixed gridl and locatedprecisely midway between them. j

7. In a pneumatic loud speaker, the combination lof an electromagnetic vibrator device having a voice coil, and an oscillator mounted for vibration by the said coil, a

ymounted for vibration by the said coil, a -sound box mounted so that it is capable of moving on an axis, an air valvev with the sound box connected with the oscillator, and means for pressing the sound box toward the vibrator device. i j 9. lIn a pneumatic loud speaker, the combination of a relatively fixed grid having substantially parallel outlet slots .for the air, a relatively movable grid with substantially parallel slots and seating on the first-named grid with the slot-s of one grid out of alignment with the slots of the other grid, and means for effecting a relative adjustment of said grids laterally with respect to the direction of the slots. y

10. In a pneumatic loud speaker, the combination of a relatively fixed grid having substantially parallel slots, a relatively movable grid seating on the same and having substantially parallel slots out of alignment, but substantially parallel with the first-named slots, a fiexible rocking plate attached to the relatively movable grid, an actuating arm attached to the flexible rocking plate, and means for adjusting the rocking plate in a direction at `right angles to the direction in which the slots extend.

11. In a pneumatic loud speaker, the combination of a rela-tively fixed grid with substantially parallel slots, a relatively movable gridwith substantially parallel slots seating on the face of the fixed grid with the slots of one lgrid out of alignment Withy the slots of the other grid, a flexible rocker plate with' means for adjusting the same in a transverse V)direction with respect to the direction' oA the slots, an actuating arm having a foot rigidly secured to the rocker plate and relatively fixed fulcrum means engaging the rocker plate adjacent the foot of the actuating arm.

12. In a pneumatic loud speaker, the combination of an air valve, an electromagnetic vibrator device-having a voice coil, an oscillator mounted for vibration by the said coil and connected with the air valve for vibrating the same, and cushion means distinct from the valvey for .dampen/ing the vibration of the oscillator. v

13. In a pneumatic loud s eaker, the combination of an air valve, anrelectromagnetic the oscillator, and cushion means for clamping the adjusting bar on both sides.

15. In a pneumatic loudspeaker, the combination of an air valve, an electromagnetic vibrator device having a voice coil, an oscillator mounted for vibration by the saidcoil and connected with the air valve for vibrating the same, a damper bar attached to the oscillator, an adjusting bar connected with the last named bar with means for nicely adjusting the same to regulate the position of the oscillator, and cushion means for clamping the adjusting bary on both sides, said cushion means comprising a pair of cushions with means for adjusting the same for clamping the adjusting bar in its different adjusted positions.

16. In a pneumatic loud speaker, the combination of an electromagnetic vibrator device having a lvoice coil, an oscillator mounted for vibration by the said coil, a sound box `With an air valve connected With the vibrator,

means for pressing the sound box toward the vibrator device, and a horn having a pliable .lsJleeve connecting the same with the sound l Signed yat Los Angeles, Calif., this 5th day of. September, 1930.

' FRANK L. HETZEL.

vibrator device having a voice coil, an oscil- Y -lator mounted for vibration by the Said coil and connected with the air valve for vibrating the same, a bar connected with the oscillator, and damper means connected with the bar and having cushion means for clamping the dampened part on both sides.

14; In a pneumatic loud speaker, the com binat-ion of an air valve, an electromagnetic vibrator device havmg a voice coil, an oscillator mounted for Vibration by the said coil and connected with the air valve for vibrat- 

